Hypodermic syringe



Nov. 28, 1967 G. COANDA 3,354,882

HYPODERMI C SYRINGE Filed Oct. 2G, 1964 1- V2 acc "2' zo-so-m-so l ll \\\" u ll lll United States Patent O 3,354,882 HYPODERMIC SYRINGE George Coanda, Glendale, Calif., assignor to Pharmaseal Laboratories, Glendale, Calif., a corporation of California Filed Oct. 26, 1964, Ser. No. 406,248 2 Claims. (Cl. 12S-218) ABSTRACT F THE DISCLOSURE A hypodermic syrin-ge having a thin-walled, expandable barrel and a permanent, enlarged expandable storage pocket formed and cooperating with a piston or stopper which includes a convex, annular traveling, seal-forming portion tapered away from an oppositelytapered discharge outlet, and in which the piston insures substantially complete exhaustion of liquid being administered with minimum resistance to piston movement and prevents leakage of liquid past the piston during its entire range of movement.

This invention relates to a disposable hypodermic syringe, and particularly to a syringe having an improved thin-walled barrel and an improved all-plastic stopper,

Rubber has been used to make hypodermic syringe Stoppers in the past because it is very resilient and seals Well within the syringe barrel. However, plastic is a more desirable material for a stopper because it does not contain vulcanizing and curing agents and is compatible with certain drugs that are deleterious to rubber as, for instance, ethyl iodophenylundecylate. Plastic Stoppers have not been widely used in the past because of their rigid nonresilient character. A plastic stopper that fits tightly enough within a barrel to prevent leakage is difficult to slide longitudinally through the barrel.

Various attempts have been made to render the plastic stopper sufficiently exible so that it can conform to the size, shape, and discontinuities of the inner barrel surface. Two such designs are described in U.S. Patents Nos. 2,902,034 and 3,135,260. However, the inherent properties of the plastic Stoppers, combined with the dimensional variations and discontinuities of the molded parts, have made leakproof syringes difficult in large quantities.

More recently, it has been proposed to use a thin ilexible-walled barrel with a plastic stopper. By thus building resilience into the barrel, many of the previous problems are remedied. This invention is described more thoroughly in an application filed June 8, 1962, by Heinz A. von Pechmann, Serial No. 201,192, entitled Plastic Syringe. However, storage must be carefully controlled to avoid a permanent deformation of the barrel which can cause leakage in subsequent use.

It is an object of this invention to provide a thermoplastic stopper which forms a hermetic sliding seal with a bore of a thermoplastic syringe barrel, which stopper slides easily in the barrel.

Another object of this invention is to provide a thermoplastic syringe that can be stored for considerable time and still be easily operable without leakage.

Another object is to provide a thermoplastic stopper configuration that slides smoothly through a syringe barrel.

Still another object of this invention is to provide a method of making a disposable thermoplastic syringe that is easily operable without leakage. Y

Other objects of this invention will become apparent upon further -description and the following'illustrations, in which:

FIGURE 1 is a perspective view, partially cut away, of the syringe barrel;

FIGURE 2 is a side elevational View, partially cut 3,354,882 Patented Nov. 28, 1967 ICC away, of the syringe showing the stopper and barrel relationship;

FIGURE 3 is a side-elevational view, partially cut away, showing the stopper longitudinally progressing through the syringe barrel;

FIGURE 4 is a fragmentary side elevational view showing the stopper as it is molded with a cylindrical sealing surface in a mold die;

FIGURE 5 is a fragmentary side elevational View of the stopper showing the stopper shape after it is cooled but before the stopper is reshaped by the syringe barrel; and

FIGURE 6 is a perspective view of the stopper.

Referring now to the drawings, syringe 1 has a barrel 2 with a bore in which a plunger 17 is axially slidea-ble. The barrel 2 has connecting means 16, which preferably is a Luer tapered adapter, associated with a partially closed end 3 for connecting the syringe to a medical device. The syringe also has a finger grip 6 adjacent an opposite open end 4 of the barrel 2. This finger grip 6 may comprise two parallel side plates 24, 24 integral with barrel wall 20, and rounded angular end walls 25, 25 connected at one end to barrel wall 20, and along their sides to side plates 24, 24. The end walls 25, 25 diverge angularly outwardly from said barrel wall 20 to provide a comfortable sloping finger gripping area. The thin cylindrical barrel wall 20 has an enlarged storage pocket 5 adjacent the partially closed end 3.

Plunger 17 includes a rigid stopper 7 in sliding engagement in the barrel bore 20, and a handle 8 which connects to stopper 7 and extends out through open end 4 of barrel 2. Handle 8 is shown as being generally X- shaped with raised rib portions 27 which closely follow the 'barrel wall 20 without excessive friction. The handle configuration insures that the stopper will align with the barrel bore and not cant to break its seal particularly When stopper 7 is near the rear o r open end of barrel 2.

The stopper 7 has a front wall 9 and a rear wall 10, which terminate at their peripheries in a leading edge 13 and a trailing edge 14, respectively. From leading edge 13 and trailing edge 14 a sealing surface 11 curves outwardly to provide a slightly convex center portion 12 for engaging the barrel wall 20 and forming a travelling seal 21 therewith. In the front wall 9 is a recess 1S concentric with and spaced radially inwardly from the leading edge 13, which recess 15 surrounds a conical nose section 18 which preferably is complementary to the partially closed end 3 of barrel 2.

Stopper 7 is much more rigid than a rubber stopper and has a larger diameter than the -bore of barrel 2. Thus, the stopper 7 temporarily expands the thin barrel wall 20 radially outwardly as it passes along the barrel to form a travelling bulge 19, as shown in FIGURE 3. The bore diameter of barrel 2 fore and aft of stopper 7 is smaller than the stopper diameter because the barrel wall 20 springs back to a smaller diameter after the stopper 7 has passed. This travelling bulge feature is similar to a snake swallowing an egg,'and a person grasping barrel wall 20 can actually feel the the travelling bulge 19 as the stopper 7 progresses along the barrel 2.

The thickness of barrel wall 20 and the amount stopper 7 diameter is greater than the bore diameter of the barrel depends on the size of the syringe which, in practice, can range between l cc. to 50 cc. capacity. For example, syringes with a maximum calibrated capacity in the range from 2 cc. to 6 cc. preferably have a wall thickness of from .015 to .040 inch and have a stopper 7 diameter that is .001 to .008 inch larger than the bore diameter of barrel 2.

With the very thin barrel Wall 20, the barrel can flex slightly outwardly or stretch to eject from a mold core pin. Therefore, the barrel can be molded with a constant bore diameter, or at least with a bore diameter that decreases no more than .0010 inch per inch of barrel length from the open end of the barrel to its partially closed end. If the bore is tapered slightly, its bore diameter is to be measured immediately rearward o'f and adjacent to the enlarged storage pocket 5. The empty storage pocket has a diameterrthat is slightly less than the stopper diameter by, for example, .0001 to .0009 inch. Thus, the storage pocket can always form a seal with the stopper.

Adjacent the partially closed end 3 of barrel 2, a unique relationship is provided between barrel wall 20 and stopper 7. The permanent enlarged storage spocket 5 receives the stopper 7 before it is used for an injection or other medical procedure. Thus, the stopper 7 can retain its diameter larger than the bore diameter of barrel 2 and form an easily slideable seal with barrel wall 20 even after long storage periods. The enlarged storage pocket 5 has a maximum diameter section which is approximately the width of sealing surface 11 and which blends smoothly into a portion of the barrel adjacent and rearward of the enlarged storage pocket 5. When the syringe 1 is used the stopper 7 is merely pulled rearwardly out of the enlarged storage pocket 5 by handle 8 and proceeds along the barrel, forming a travellingbulge 19. For the purposes of illustration, the enlarged storage pocket 5 and travelling bulge 19 have been exaggerated throughout the drawings. As in the thickness of barrel wall 20 and the differences between the stopper 7 diameter and barrel 2 bore diameter, the difference between the diameter of the enlarged storage pocket 5 and adjacent portion of barrel 2 varies with sizes of syringes from 1 cc. to 50 cc. capacity. For a syringe with a maximum calibrated jcapacity in the range of 2 cc. to 6 cc., the enlarged storage pocket diameter is preferably from .001 to .008 inch larger than the bore of an adjacent portion of barrel 2.

No leakage occurs in the enlarged storage pocket 5 despite its larger diameter than the adjacent portion of the barrel because of a shifting seal feature of this invention. When stopper 7 travels along barrel 2l it forms the seal 21 at a center portion 12 of the slightly convex sealing surface ll'of stopper 7. Although the seal 21 is only formed when stopper 7 is in barrel 2, for illustrative purposes the position of this seal is shown on the stopper in FIGURE 6. As the stopper 7 approaches partially closed end 3 of barrel 2, it drops into the enlarged storage pocket 5. As this happens the hermetic `seal 21 shifts without leakage to the leading edge 13 of stopper 7, where it forms a very thin line contact betweenthe leading edge 13 and partially closed end 3 of barrel 2.*Preferably, leading edge 13 contacts partially closed end 3 before the conical nose section 18 when the stopper falls into enlarged storage pocket 5, thus insuring a contact with partially closed end 3 for the shifting seal. This shifting seal feature is easily observed through the transparent barrel wall 20.,

The method of making the syringe of this invention involves the steps of molding the thin wall barrel and molding the stopper 7 with a front wall 9 and a rear wall 10, each of which terminates at its periphery in its respective leading and trailing edges 13'and 14.4 Leading edge 13 and trailing edge 14 are molded of substantially the same diameter so the sealing surface forms a nontapered cylinder. This is shown in FIGURE 4 wherein mold die 26 is a part of a cam actuated mold which can integrally mold stopper 7 and handle 8 as a one-piece plunger 17. The parting lines indicate the parting lines of the mold. The front wall 9 of stopper 7 is molded with a recess 15 that is concentric with andy spaced from leading edge 13, and which surrounds a conical nose section 18. Following the molding steps, the stopper 7 is cooled whereby trailing edge 14 shrinks more than leading edge 13, thereby giving a slight frusto-conical shape to the stopper 7, as shown in FIGURE 5. This cooling step is preferably carried out with an integral handle 8 connected to the rear wall 10 of the stopper 7, to give a greater mass of thermoplastic at rear wall 10, causing it tQ Shllll {H Qfe, than. f fQKlt Wall 9. Recess 15 also aids in causing leading edge 13 to shrink less than trailing edge 14.

Next, the plunger 17 is placed in the barrel 2 with the stopper 7 positioned adjacent the partially closed barrel end 3. As previously indicated, the stopper 7 exerts a radially outward force against the portion of the barrel adjacent to closed end 3, a'nd thus causes a temporary deformation of the barrel. The syringe is then stored with the stopper in this position so that the deformed barrel portion takes a permanent set, thus forming a permanent enlarged storage pocket 5. While the stopper 7 is stored adjacent partially closed end 3, the syringe can be sterilized by a gas, such as ethylene oxide, at temperatures from F. to 120 F., and these elevated temperatures hasten the formation of the permanent enlarged storage pocket 5. During the storage step the frusto-conical sealing surface of stopper 7 as shown in FIGURE 5 simultaneously and permanently deforms adjacent the leading and trailing edges 13 and 14 to form a slightly convex sealing surface 11 with a center portion 12, as shown in FIGURES 2, 3, and 6.

The stopper 7 remains in enlarged storage pocket 5 until the syringe is ready to use, at which time stopper 7 is pulled rearwardly through barrel 2 with a smooth, easy motion.

The entire syringe herein described is made of thermoplastic materials. Any thermoplastic may be used forbarrel 2 that can be molded into a thin transparent wall which can flex radially outwardly as herein described. I lhave found that polyoleris, as for example polypropylene, work very well for the barrel material. The plunger 17 iS preferably molded as a single piece of a material sufficiently rigid to form a handle 8 that will move stopper 7 in the barrel when axial force is applied to the handle, whereby stopper 7 will push barrel wall 20 radiallyv outwardly into a travelling bulge 19. A polyolen, for example linear polyethylene, works very Well for the plunger.

While I have described my invention with specific examples, those skilled in the art can make certain changes without departing from the spirit and scope of this invention.

I claim:

1. A hypodermic syringe comprising: a thin-Walled thermoplastic `barrel with a front wall having an inner frusto-conical surface sloping toward a central discharge opening; and a thermoplastic stopper suiciently rigid to create a traveling sealing-bulge progressively along said thin-walled barrel as the stopper slides along the bore of said barrel, said stopper lhaving a 'rear wall and a front wall respectively bounded by peripheral trailing and leading edges, said edges having disposed therebetween a convexly curved sealing surface tapering rearwardly substantially from said leading to said trailing edge, said stopper having a centrally located, forwardly tapered nose portion, said barrel having a deformable pocket with an internal surface that is permanently bulged outwardly regardless of the position of said stopper in said barrel bore, said pocket being immediately adjacent the inner frustoconical barrel surface and substantially bounding the rearward margin thereof, the largest diametrical portion of said rearwardly tapered convex sealing surface of said stopper progressively bulging said deformable pocket un- 'til the stopper seats at the rear margin of the inner 'frustoconical surface of said barrel, said deformable pocket having an inner surface configuration complementary to the outer periphery configuration of said stopper, said forwardly tapered nose portion being so conformed inrelation to the said stopper leading edge so as to permit said leading edge to completely move through said pocket in sealed relation and ultimately seat at the rear margin of said frusto-conical barrel surface.

2. The structure las claimed in claim 1 in which the outer surfaceof said tapered nose portionis parallel to the 5 6 frusta-conical inner surface of the front wall of said 3,013,557 12/ 1961 Pallotta 128-218 barrel. 3,253,592 5/ 1966 Von Pechmann 128-218 References Cited FOREIGN PATENTS UNITED STATES PATENTS 5 223,386 8/ 1959 Australia.

1,948,982 2/1934 Cutter 12s- 21s D- L- BAKER AsssmmExamine 2,575,425 11/ 1951 Nelson 128-218 RICHARD A. GAUDET, Primary Examiner. 

1. A HYPODERMIC SYRING COMPRISING: A THIN-WALLED THERMOPLASTIC BARREL WITH A FRONT WALL HAVING AN INNER FRUSTO-CONICAL SURFACE SLOPING TOWARD A CENTRAL DISCHARGE OPENING; AND A THERMOPLASTIC STOPPER SUFFICIENTLY RIGID TO CREATE A TRAVELING SEALING-BULGE PROGRESSIVELY ALONG SAID THIN-WALLED BARREL AS THE STOPPER SLIDES ALONG THE BORE OF SAID BARREL, SAID STOPPER HAVING A REAR WALL AND A FRONT WALL RESPECTIVELY BOUNDED BY PERIPHERAL TRAILING AND LEADING EDGES, SAID EDGES HAVING DISPOSED THEREBETWEEN A CONVEXLY CURVED SEALING SURFACE TAPERING REARWARDLY SUBSTANTIALLY FROM SAID LEADING TO SAID TRAILING EDGE, SAID STOPPER HAVING A CENTRALLY LOCATED, FORWARDLY TAPERED NOSE PORTION, SAID BARREL HAVING A DEFORMABLE POCKET WITH AN INTERNAL SURFACE THAT IS PERMANENTLY BULGED OUTWARDLY REGARDLESS OF THE POSITION OF SAID STOPPER IN SAID BARREL BORE, SAID POCKET BEING IMMEDIATELY ADJACENT THE INNER FRUSTOCONICAL BARREL SURFACE AND SUBSTANTIALLY BOUNDING THE REARWARD MARGIN THEREOF, THE LARGEST DIAMETRICAL PORTION OF SAID REARWARDLY TAPERED CONVEX SEALING SURFACE OF SAID STOPPER PROGRESSIVELY BULGING SAID DEFORMABLE POCKET UNTIL THE STOPPER SEATS AT THE REAR MARGIN OF THE INNER FRUSTOCONICAL SURFACE OF SAID BARREL, SAID DEFORMABLE POCKET HAVING AN INNER SURFACE CONFIGURATION COMPLEMENTARY TO THE OUTER PERIPHERY CONFIGURATION OF SAID STOPPER, SAID FORWARDLY TAPERED NOSE PORTION BEING SO CONFORMED IN RELATION TO THE SAID STOPPER LEADING EDGE SO AS TO PERMIT SAID LEADING EDGE TO COMPLETELY MOVE THROUGH SAID POCKET IN SEALED RELATION AND ULTIMATELY SEAT AT THE REAR MARGIN OF SAID FRUSTO-CONICAL BARREL SURFACE. 